This application claims foreign priority of French application 00/15549, filed Nov. 30, 2000.
The present invention relates to a use of sterols as active principle in a cosmetic composition to combat adiposity and thus refine the silhouette.
Sterols are known for their use as active substance in anti-inflammatory medications in which they act as inhibitors of lipoxygenase. One may refer to the patent document FR-A-2 705 030 which shows such an activity.
They are also known for cosmetic compositions for treatment of the skin in which they act as emollients by presenting good properties of moisturizing and barrier. Document U.S. Pat. No. 4,604,281 shows such a use.
Concerning cosmetic compositions to combat adiposity, one is acquainted with those of which the active principles used present a lipolytic activity by which they stimulate the degradation (or lysis) of the fats stored in the human adipocytes, in particular in the form of triglycerides, and promote the elimination of the products of that degradation, in particular fatty acids and glycerols. For example, theophylline and isoproterenol are known to stimulate the lipolysis of triglycerides, in particular triglycerides of human adipocytes.
Moreover, in the French patent document No. 98 02152, the active principle used to stimulate lypolysis is a pyrone group which has the effect of activating the phosphorylation of a lipase enzyme for the degradation of the triglycerides in fatty acids. This pyrone group is, for example, mangosteen extracted from a tree of the Garcinia mangostana species.
One is also acquainted with cosmetic compositions the active principle of which is not to stimulate the lipolysis of triglycerides of human adipocytes but to inhibit the lipogenesis of these triglycerides.
It is to be recalled here that, in the adipocytes, lipolysis is in competition with lipogenesis which consists in the formation of fats, in particular triglycerides, and which brings into play an entire series of biochemical reactions bringing about the action of proteins with enzymatic activity such as Acyl-CoA synthetase and fatty acid synthetase, which are also known under the name FAS (fatty acid synthase).
Cerulenine is a compound which is known to inhibit lipogenesis by inhibition of the FAS synthetase.
In a previous patent application, it was also shown that the same is true with eicosapentanoic acid (EPA).
It has now been discovered that sterols which come from a plant or algae extract have, on the one hand, an inhibitory activity for lipogenesis of triglycerides produced by human adipocytes and, on the other hand, an activity stimulating the lipolysis of the same substances.
The invention therefore has as object the use of sterols from a plant or algae extract as active substance in a cosmetic composition to combat adiposity.
It is thought that the sterols that are contained in the said extract are responsible for an inhibitory effect on the action of an enzyme that plays a part in lipogenesis, in particular the synthesis of fatty acids by fatty acid synthetase FAS. Thus, by using a cosmetic composition that contains sterols as active principle, the lipogenesis of these fatty acids is inhibited or at the very least limited and their concentration in the adipocytes is thus reduced.
We were able to show below that most particularly campesterol and beta-sitosterol, generally present in plants or algae, have this inhibitory action.
It is to be understood that the cosmetic compositions that are planned to inhibit this lipogenesis make it possible to avoid the instantaneous recovery of the fat lost after lipolysis.
It is also thought that the sterols have a direct effect on the lipolysis of the triglycerides of human adipocytes by stimulating it.
We were able to show below that this is particularly true concerning the stigmasterol derived from a plant or algae extract.
It is to be understood that the cosmetic compositions that are planned to stimulate lipolysis have a direct curative effect by reducing excess fat.
It is also thought that sterols have an inhibitory effect on the differentiation of adipocytes. In fact, it has been demonstrated that steroid hormones (estrogens and androgens) regulate the differentiation of adipocytes, that is to say the maturation of dermic cells (fibroblasts) into cells capable of accumulating fat in the form of triglycerides.
Moreover, androgens such as testosterone, dihydrotestosterone (DHT), dehydroepiandrosterone (DHEA), androstanediol and androstenediol have an inhibitory effect on the differentiation of adipocytes, in particular by the inhibition of the activity of the enzyme glucose-6 phosphate dehydrogenase, while the action of the estrogens like beta-estradiol is expressed by a modulation of the expression of receptors like that of IGF1 (insulin growth factor 1).
During differentiation, the size of the cells and the fat content increase greatly, and xe2x80x9cmarkersxe2x80x9d also appear, such as, for example, an increase in expression of enzymes like lipoprotein lipase (LPL), a decrease in enzymatic activity like that of glycerol 3-phosphate dehydrogenase, an increase in the expression of membrane proteins like the fatty acid transporter (FAT), an increase in the expression of transcription factors of the genes of lipogenesis like the peroxisome proliferator-activated receptors (PPARs) or the CCAAT/enhancer-binding proteins (C/EBPs), and an increase in the quantity of intracellular proteins like p18 (INK4c), p21 (Waf1) or aP2 (adipocyte fatty acid binding protein or FABP).
It may therefore be thought that the effect of phytosterols is expressed by an effect on the differentiation of pre-adipocytes into adipocytes (anti-adipogenic effect), in addition to the inhibitory effect on lipogenesis and the lipolytic effect.
The cosmetic compositions that are planned for inhibiting the differentiation of adipocytes will have a preventive effect by preventing the development of excesses of fat.
According to the present invention, the extract containing at least one sterol is an oily extract obtained from seeds of Polygonum fagopyrum. 
The present invention also relates to a preparation process of a substance that contains as active principle a lipidic extract of plants or algae containing sterols.
We will now describe the procedure of the experiments that were conducted to prove the effect of sterols derived from an extract of plants or algae on lipids.
In these experiments, adipocytes were isolated from abdominal restorative surgeries sampled in women. The experiment took place the day of the sampling. Fragments of adipose tissues were incubated for 30 minutes at 37xc2x0 C. in the presence of collagenase, then the isolated adipocytes were washed and taken up in medium MEM buffered with bicarbonate, in the presence of antibiotics (penicillin/streptomycin), glutamine (2 mM), and delipidated bovine serum albumin (0.5%).
The tests concerning the effect on lipogenesis were then conducted in the following manner.
Adipocytes (90 xcexcl of xc2xc diluted suspension) were incubated for 1 hour, either with a control medium (4 hours), with molecules known to inhibit the neosynthesis of fatty acids (EPA), as for example insulin, or with previously diluted extracts (added under 100 xcexcl).
As to the sterols and to the lipidic extracts of plants or algae, they were diluted in mineral oil which has been verified to not inhibit incorporation or extraction of adipocyte lipids. Then, 10 xcexcl of [214C]-acetate, 50 xcexcCi/ml, were added, and the samples were either cultivated at 37xc2x0 C. in the presence of 5% CO2 for 4 additional hours, or immediately frozen at xe2x88x9280xc2x0 C. (control t0).
Each experiment was carried out in duplicate insofar as the test proved to be reproducible and with low standard deviations.
At the times indicated, the samples were frozen at xe2x88x9280xc2x0 C. The lipids were then extracted according to the method of Bligh and Dyer (extraction methanol/chloroform/water), then dried under nitrogen. The radioactivity incorporated was then counted by liquid scintillation.
As to the tests concerning the effect on lipolysis, they were conducted in the following manner. Adipocytes (540 xcexcl of suspension) were incubated for 2 hours in a water bath at 37xc2x0 C., with agitation, in the presence of 60 xcexcl of different sterols. The experiments were carried out in triplicate.
Then, the non-esterified fatty acids (AGNE) released by the adipocytes were determined in the sub-adipocyte media. The values obtained were treated by an analysis of variance (ANOVA) by means of the multiple comparison test of Dunnett. The values were considered as significant when the probability p was less than the threshold of significance 0.05.